At first I thought the question was for deep or shallow frying chicken, but I think you're asking about stir-frying. My tips:
1. Before slicing the chicken for stir fry, freeze it for 15-20 min. to harden it up - this will make it easier to cut thin slices
2. Slice thinly and evenly. Try to make 1 mm slices. Leave in slices or cut into small pieces as desired for your dish.
3. Marinade as you normally would (for example, soy sauce with cooking wine and corn starch, etc.)
4. When stir frying, Heat up the pan with some oil (depending on size of pan but 2 Tbs. is probably a good amount). When the oil starts to shimmer and perhaps whisps of smoke appear, it's ready. If it really starts to smoke, you've waited too long and over heated your oil - start the pan over.
5. Lay the chicken pieces down onto the hot pan and if any pieces are folded over or clumped, break them up and spread them with a wooden spoon or other utensil. If it's too much chicken to do in one layer then cook the chicken in several batches (THIS IS IMPORTANT). The chicken will cook very fast this way, so multiple batches doesn't really increase the time. Not doing it in multiple batches will definitely result in overcooked chicken because by the time all the chicken reaches temperature, the rest of the chicken is overdone.
6. Wait a minute and once the chicken pieces are starting to cook, you can toss them around the pan and start them moving. With a hot pan, they should all be done after another minute or so. If liquid starts to pool in the pan, then either your pan is not hot enough or your trying to cook too much chicken at the same time. All the liquid should evaporate quickly, so you don't end up poaching the chicken.
7. Remove the chicken from the pan when it's done. Cook the rest of the stir fry components (vegetables, etc.) and as the last step, toss the chicken and sauce in to complete the dish.[/list][/list]

In order to answer your question on burner settings, you will have to experiment a bit. All other things being equal, I have several standard settings for different pans on my electric stove.

Cast iron skillet - medium high
Calphalon stir fry pan - a touch over medium
Cuisinart saute pans - right between medium and medium low. If I set to medium, I have to listen to my smoke detector.

A recommendation on "heating a pan with oil": Pre heat the pan dry. You can let the pan sit on the burner almost indefinitely while you do some final prep work and have no issues. Once you add oil, you are committed and need to cook and do nothing else. When you are ready, add your oil and let it heat for 10-20 seconds (until it shimmers, wisps of smoke along the edges) and then your food. Some people recommend removing the pan from the heat when adding oil to minimize flare-ups. YMMV.

This technique does 3 things for me:
1) Gets the pan up to temp. I am impatient and tend to add the food before the pan is heated thoroughly otherwise.
2) Encourages me to double-check my mis en place before food is in the pan. (Oil, check, salt, check, etc)
3) Allows me to use water to "sprinkle test" the pan temperature before adding the oil. Put a drop or two of water into the pan and observe its behavior. If it just sits there, the pan is too cold. If it skitters around or immediately turns to steam it's way too hot. Again, your results may be different. Experimentation is key.

Traditional stir-fry is done over the highest heat possible with meat sliced so thin you can see through it. It should take less than 90 seconds for the meat to cook through (cook first, separately from the veggies), and there should be no liquid in the pan, else you are 'steam frying'. The trick for tender stir-fry beef beef is to sprinkle the slices with baking soda and let sit for 20 minutes or so then rinse, might want to try it with the chicken, though it may tenderize to mush.